Scavenging internal-combustion engine



E. HEW??? SCAVENG-ING INTERNAL COMBUSTION BNGINE'I Filed April 5. i936Patented Apr. 3, 1928.

- UNITED STATES 1,664,817 PATENT orrlcs.

ERNST HERKT, OF KIEL, GERMANY, ASSIGNOR TO FRIED. KRUPP GEBKANI-A WERFTAKTIENGESELLSGHAIT, OF KIEL-GAABDEN, GERMANY.

SCAVENGING INTERNAL-COMBUSTION ENGINE.

Application filed April 3,

The invention relates to two stroke cycle double-acting internalcombustion engines which are scavenged by means of ports. In scaven ingsuch engines difiiculties arise especizfily on the lower (piston rod)side oi the cylinder, as here the piston rod forms an obstacle for acontinuous course of the scavenging air current due to its unfavorablecircular cross section.

The simplest and most satisfying scavenging effect would be attainedwith such engines by the adaption of the well-known socalled crossscavenging method, as illustrated in Fig. 1, with which method thescavenging air entering on one side of the cylinder A throu h admissionports C is directed into para lcl with the cylinder wall by a bafilelateI) provided on the piston and after aving struck the piston rod, leavesthe'cylinder through exhaust ports D diametrally opposite to saidadmission ports C, as with this method the scavenging current strikesthe piston rod" but once, viz, at w. This method, however, suffers fromsome drawbacks, in particular due to the bafile plate I) whichnecessarily must be arranged on the end face of the piston and isundesired by certain reasons, and due to the forced double rectangulardeflection of the so entering and escaping scavenging current, so

that this method recently has been abandoned and the so-called reversemethod, likewise well-known, has been adopted. With this method thescaven 'ng air passes the piston end 'face in a close current, flowsalong the opposite cylinder wall up to the c linder cover and returns onthe entrance side where it esca es through exhaust ports which aresituate on this side nearer to the o cylinder coventhan the admissionports. This scavenging method is illustrated in Figs. 2 and 3 as adaptedto the iston' rod side of the cylinder. This me od, however, shows fromthe first the drawback of the 46 scavengin current striking the istonrod on two p aces, viz, at a: and y, ig. 2. It has been proposed,therefore, in order to attain in some measure, at least on the pistonend face, a shockless passage 50 ing current, to so direct the admissionrts, see Fig. 3, that the scavenging air wi 1 not strike the piston roddirectly and the branch currents unite again on the opposite side andascend and so on. This measure, however,

of the scaveng said 1926, Serial No. 99,510, and in Germany April 3,1925.

is likewise not capable of securing a continuous and eddilcss course ofthe scavenging current. For, as clearly will be 'seen from Fig. 3, thebranch currents entering the cylinder through the groui of ports 0',meet the branch currents intro uced through the group of ports 0 under arather large angle, this causing disturbing eddies to arise behind thepiston rod. Furthermore, this scavel'iging method has the drawback ofthe entering and escaping scavenging currents closely passing each otherin counter-current on the admission and exhaust ports. In consequencethereof violent eddies will arise on this lace too, causing the admittedfresh scavenging air to be immediately withdrawn again from thecylinder, a'loss in scavenging air thus being unavoidable.

Now my invention has for its object to create a scavenging means, inparticular adapted to be used on the piston rod side of two stroke cycledouble-acting internal combustion engines, by means of which theabove-mentioned drawbacks are obviated and the scavenging air currentmust pass the piston rod but once, as in the cross-scavenging methodshown 1n Fig. 1.

An embodiment of: the subject-matter of my invention is illustrated byway of example in the drawing which accompanies and forms part of thisspecification.

In this drawing:

Figs. 1 and 2, are vertical sections in diagrammatic form of 2 forms ofpiston and cylinder arrangement according to the prior art.

Fig. 3 is a cross section of line 3-3, of

Fig 2.

ig. 4 is a fragmentary lon tion through the working cy internalcombustion engine, Fig. 5 is the cross section on itudinal secmder of anline 5-5 of 1g. 6 is the cross section on hne 6-6 of Fii 5.

denotes the working cylinder of a two stroke cycle double-actinginternal combustion engine and B the piston reciprocating therein andhaving an end face I) tapering towards the piston rod E. I provide agroup of admission ports 0 on both sides of cylinder A and a group ofexhaust ports D. ports C, D being situated on a common level. Both saidgroups of ports are inclined in the direction of the angle ofthe taperedpiston end face I), see Fig. tfthe exhaust ports D penetrating thecylinder -wall in radial direction, see Fig. 5, while the admissionports C are arranged so as to cause the branch currents enteringtherethrough to arrive behind the piston rod.

By the described arrangement and direc- "tion of the admission andexhaust ports C,

D in combination with the described shape of the piston end face 6 Iattain that the branch currents entering through the admission ports Care guided, after having passed.

these ports, by the tapered piston end face 6 within the cylinder up inthe manner shown in Fig. 4, and unite, without any formation of eddies,so as to "form a closed scavenging current which rises along thecylinder Fwall, branches near the cylinder cover so as toembrace thepiston rod, thereupon is guided downwardly in a closedcondition alongthe oppositecylinder wall and finally is deflected by said taperedpiston end face 6 so as to continuously escape tln'oughthe exhaust portsI). I- attain in this manner that the scavenging air entirely obviatesthe obstacle formed by thev piston rod and meets it but once, viz, onthe cylinder cover, as in the wcll-knmvnscavenging method illustrated inFig. 1. I further attain thatthe scavenging air is guided satisfactorilyand continuously during the whole scavenging period and leaves thecylinder in a quietly flowing current, all portions of the cylinderbeing met by the scavenging air. Of course the generatrix of the taperedend face 6 of the piston might be formed by a suitable curve thecurvature of which, however, must subside in a continuous course intothe line of inclination ofthe admission and exhaust ports.

I claim:

Two'cycle internal combustion engine of the Diesel type, comprising acylinder, a piston Working therein having a piston rod penetrating thecylinder room and an end face tapering towards the piston rod, pistoncontrolled inlet ports arranged at both sides of the cylinder and outletports arranged at one side of the cylinder between the inlet ports andat the same level with the inlet ports, said inlet ports being inclinedsothat theincoming scavenging air flows tangent the tapered end face ofthe piston on both sides and strikes the cylinder wall opposite to theoutlet ports, the two flows of the scavenging air uniting and beingdirected along said wall to the cylinder head crossing the piston rodand flowing to the outlet ports, said outlet ports being inclined at thesame angle as the tapered fa ce of the piston rod.

The foregoing specification signed. at Hamburg, Germany, thistwenty-fifth day .of February, 1926.

ERNST HERKT.

